1. Field of the Invention
This invention relates to an exposure control system for a photographic camera, and more particularly to a program control type exposure control system for a dual priority automatic exposure control camera.
2. Description of the Prior Art
In the conventional automatic exposure control cameras, there are aperture priority and shutter speed priority automatic exposure control cameras. Further, there are also known program control type exposure control cameras in which both the aperture and the shutter speed are controlled.
The conventional single lens reflex cameras provided with an automatic exposure control system are based on one of the above three known systems. These exposure control systems are, however, disadvantageous in that it is impossible to freely select a desired one of the exposure factors, i.e. aperture or shutter speed. Therefore, it has recently been developed to provide a dual priority automatic exposure control camera in which a desired one of the aperture and the shutter speed can be selected in advance and the other is automatically controlled. In such a dual priority automatic exposure control camera, a memory means like ROM of a micro-computer is employed to provide memorized combinations of shutter speed and aperture size to conduct a program control of exposure. Therefore, the structure of the exposure control mechanism is complex and the manufacture thereof is difficult as well.